Define nitrogen estimation - kjeldahl''s method, Biology

Assignment Help:

Define Nitrogen Estimation - Kjeldahl's Method?

Nitrogen in the protein is estimated by a method referred to as Kjeldahl's method. Although over a period of time many other methods have emerged for determination of organic nitrogen, this method still remains an old favourite because it is reliable and has very well standardized procedures. The method involves the digestion of the weighed sample with concentrated sulphuric acid, selenium oxide, potassuim sulphate and copper sulphate in a long necked special digestion flask known as kjeldahl's flask. Potassium sulphate increases the boiling point of the mixture. Since the digestion results in fuming of the sulphuric acid, the procedure has to be carried out in a fume hood and the procedure takes several hours. The sample is digested until the solution in the digestion flask becomes clear after which it is transferred to an appropriate volumetric flask (usually 50 or 100 ml flask) and the volume is made up to the mark with distilled water. Aliquots of this sample are used for distillation in the kjeldahl's apparatus and nitrogen in the protein is estimated. Most proteins contains 16% nitrogen. Thus, percent nitrogen content is multiplied by 6.25 to get crude protein content.

1805_Nitrogen Estimation - Kjeldahl’s Method.png

The experiment involves decomposition of ammonium sulphate by a fixed volume of alkali (NaOH). Ammonium sulphate on decomposition releases ammonia which is collected in a flask of boric acid solution Tashiro's indicator. With boric acid ammonia forms a complex 'ammoium borate'. As ammonia is distilled into the boric acid, the Tashiro indicator slowly changes colour from pink to green. This is because the colour of the indicator is pH dependent - it is pink in acidic medium and green in alkaline medium. When the green coloured solution containing the boric-acid-ammonia complex is retitrated against H2SO4, the solution slowly becomes acidic again and the indicator becomes pink. This point when colour changes from green to pink is taken as the end point.


Related Discussions:- Define nitrogen estimation - kjeldahl''s method

What is osteoblast, What is osteoblast The osteoblast is the key for th...

What is osteoblast The osteoblast is the key for the development of new bone. It is essential that a large number of osteoblasts accumulate on the implant surface(contact osteo

Determine the term epitheliomuscular cell, Determine the term Epitheliomusc...

Determine the term Epitheliomuscular cell. Cells which line outer surface of cnidarians. These cell have two functions: first is to form the outer body covering of animal, seco

State about the blood-aqueous barrier, State about the blood-aqueous barrie...

State about the blood-aqueous barrier There is a blood-aqueous barrier which prevents the movement of substances from the plasma to the aqueous humour. If there is a breakdown

Transcription and processing of prokaryotic rrna, In E.  coli  there  are  ...

In E.  coli  there  are  seven  rRNA  transcription  units  scattered  by  the genome,  each of that contains one copy of every of the 16S, 23S  and 5S rRNA genes and one to four c

Define biochemistry, Biochemistry : The chemistry  of  living organisms ...

Biochemistry : The chemistry  of  living organisms that covers all  the chemical reactions occurring  in our body.

Types of nitrogen wastes excreted by living beings, Q What are the three ma...

Q What are the three major types of nitrogen wastes excreted by living beings? The main nitrogen wastes excreted by living beings are ammonia, urea and uric acid. Living beings

Show species with exoskeleton, Q. Which other phylum of the animal kingdom ...

Q. Which other phylum of the animal kingdom present species with exoskeleton? Arthropods present exoskeleton made of chitin. Echinoderms do not have exoskeleton but they presen

Display schematically and give all data, Through Nuclear transfer how Dolly...

Through Nuclear transfer how Dolly came into the picture. Show schematically and give all data.

What is the salivary digestive enzyme, Q. What is the salivary digestive en...

Q. What is the salivary digestive enzyme? Which type of food does it digest and into which smaller molecules does it transform the food? The salivary hydrolase is known as sali

What are polyclonal antibodies, Antibodies of dissimilar specificities, whi...

Antibodies of dissimilar specificities, which react to the same antigen, are known as polyclonal antibodies.

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd